1. Field of the Invention
The present invention relates to methods of automatically setting document registration and locating a calibration strip in an image inputting machine, and in particular to methods of automatically setting document registration and locating a calibration strip in an image inputting machine which includes an electronic scanner for reading data from a document and transforming that data into digital signals which can be stored and/or analyzed.
2. Description of Related Art
Traditionally, Universal Document Handlers (UDH) used with copiers or image inputting machines require mechanical adjustment of mirrors, scan carriage assemblies, or other assemblies to adjust document registration. One such mechanical adjustment involves setting the document registration so that the scan carriage which inputs data contained on the documents begins its scanning traversal of the document at an edge of the document. Another adjustment, required with electronic scanners, involves location of a calibration strip which is used to calibrate the Charge Coupled Devices (CCD) which typically make up the scanning array.
Difficulties in automatic document handling systems in general are discussed hereinbelow. These difficulties include the criticality of document registration and the need for increased automation and operator simplification especially with current increases in document handling speeds.
As xerographic and other copiers increase in speed, and become more automatic, it is increasingly important to provide higher speed yet more reliable and more automatic handling of the document sheets being copied, i.e. the input to the copier. It is desirable to feed, accurately register, and copy document sheets of a variety or mixture of sizes, types, weights, materials, conditions and susceptibility to damage, yet with minimal document jamming, wear or damage by the document transporting and registration apparatus, even if the same documents are automatically fed and registered repeatedly, as for recirculating document precollation copying.
The art of original document sheet handling for copiers has been intensively pursued in recent years. Various systems have been provided for automatic or semiautomatic feeding of document sheets to and over the imaging station of the copier for copying. The documents are normally fed over the surface of an imaging station comprising a transparent platen, into a registered copying position on the platen, and then off the platen. Such automatic or semiautomatic document handlers eliminate the need for the operator to place and align each document on the platen by hand. This is a highly desirable feature for copiers. Document handlers can automatically feed documents as fast as they can be copied, which cannot be done manually with higher speed copiers, thus enabling the full utilization or productivity of higher speed copiers.
A preferable document handling system is one that utilizes an existing or generally conventional copier optical imaging system, including the external transparent copying window (known as the platen or imaging station) of the copier. It is also desirable that the document handling system be readily removable, as by pivoting away, to alternatively allow the copier operator to conventionally manually place documents, including books, on the same copying platen. Thus, it is desirable that a document registration edge alignment or positioning system be available for such manual copying which is compatible with that used for the document handler.
One of the most difficult to achieve features for automatic document handling is the rapid, accurate, reliable, and safe registration of each document at the proper position for copying. Conventionally the document is desirably either center registered or corner registered (depending on the copier) by the document handler automatically at a preset registration position relative to the copier platen. At this registration position, two orthogonal edges of the document are aligned with two physical or positional (imaginary) registration lines of the copier platen at which the original document is properly aligned with the copier optics and copy sheet/photoreceptor registration system for correct image transfer of the document image to the photoreceptor and then to the copy sheet. This registration accuracy is desirably consistently within approximately one millimeter. If the document is not properly registered, then undesirable dark borders and/or edge shadow images may appear on the ensuing copy sheet, or information near an edge of the document may be lost, i.e. not copied onto the copy sheet. Document misregistration, especially skewing, can also adversely affect further feeding and/or restacking of the documents.
In preferred types of copying systems the document is registered for copying overlying a selected portion of a full sized (full frame) platen which is at least as large as the largest document to be normally copied automatically. In such systems the document is preferably either scanned or flashed while it is held stationary on the platen in the desired registration position. That is, in these full frame systems the document is preferably registered by being stopped and held during imaging at a preset position over the platen glass which is adjacent one side or edge thereof.
As shown in the art, and further discussed below, document handling systems have been provided with various document transports to move the documents over the copier platen and into registration. Such document platen transports may comprise single or plural transport belts or feed wheels, utilizing frictional, vacuum, or electrostatic sheet driving forces. Various combinations of such transports are known with various registration devices or systems. Preferably the same platen transport sheet feeder is used to drive a document onto and off of the platen before and after copying as well as registering the document.
The present invention is particularly suitable for precollation copying, i.e. automatically plurally recirculated document set copying provided by a recirculating document handling system or "RDH". However, it also has applicability to nonprecollation, or postcollation, copying, such as postcollation operation of an RDH or semiautomatic document handling (SADH). Postcollation copying, or even manual document placement, is desirable in certain copying situations, even with an RDH, to minimize document handling, particularly for delicate, valuable, thick or irregular documents, or for a very large number of copy sets. Thus, it is desirable that a document handler for a precollation copying system be compatible with, and alternatively usable for, post collation and manual copying as well.
Some examples of Xerox Corporation RDH U.S. Patents are U.S. Pat. No. 4,459,013 issued July 10, 1984 to T. J. Hamlin et al; U.S. Pat. No. 4,278,344 issued July 14, 1981 to R. B. Sahay; and U.S. Pat. Nos. 4,579,444, , 325 or 326. Some other examples of recirculating document handlers are disclosed in U.S. Pat. Nos. 4,076,408; 4,176,945; 4,428,667; 4,330,197; 4,466,733 and 4,544,148. A preferred vacuum corrugating feeder air knife, and a tray, for an RDH, are disclosed in U.S. Pat. Nos. 4,418,905 and 4,462,586. An integral semiautomatic and computer form feeder (SADH/CFF), which may be an integral part of an RDH, as noted in col. 2, paragraph 2, therein, is disclosed in U.S. Pat. No. 4,462,527. Various others of these patents, such as U.S. Pat. No. 4,176,945 above, issued Dec. 4, 1979 to R. Holzhauser (Kodak) teach plural mode, e.g. RDH/SADH, document handlers.
Regardless of the type of document handler used, or whether any document handler is used, the scan carriage must be properly aligned with the registration positions of documents on the platen. This alignment has been done in the past by determining the amount of adjustment needed to compensate for misalignment between the registration position to which a document is positioned (either manually or by a document handler) and the scan carriage start position, and manually adjusting either the scan carriage (or copier) or the document handler so that the registration position of the document and the initial scan carriage position are aligned. Since it is desirable to use a type of document handler that includes structure for feeding documents automatically from an RDH input and semiautomatically from an SADH input, (the SADH input also being capable of receiving computer fan folds (CFF)) which document handler locates sheets at different positions on the platen depending on whether the sheets are fed from the RDH or SADH inputs, up to three separate adjustments must be made in order to align the scan carriage with the registration positions of documents
Additionally, since it is desirable to use a document handler which is compatible with a variety of different copying machines or input scanners (known as universal document handlers (UDH)), it is desirable to provide an input scanner which can adjust itself to the document registration positions of the UDH so that production tolerance in the manufacture of the UDH and input scanner need not be coordinated with each other with high tolerances. It is also desirable to provide a system for registering a document scanner to sheets placed on a platen which does not require every sheet to be prescanned since prescanning slows down the throughput of the scanner.
U.S. Pat. No. 4,831,420 to Walsh et al. discloses a system for setting or adjusting the proper registration position of the original documents in a copier having a document feeder providing a variable document registration position on the platen, and numeric data key entries in specialized diagnostic modes, and non-volatile memory. The system involves registering and copying a test sheet using the document feeder in its initial, unadjusted, registration setting. The test sheet has a test pattern of registration position indicia with identifying numeric indicia, and also includes a registration window at an optically reversed position on the test sheet from the test pattern and a cursor pointing to a specific position within the window. The test sheet is laid over a same-size copy of the test sheet, with the sheet edges aligned, but with the two sheets rotated by 180.degree. relative to one another, so that the copy of the test pattern on the copy sheet underlies and is visible through the registration window of the test sheet, whereby the cursor on the test sheet points to a specific registration identifying numeric indicia within the test pattern copy. The copier resets in non-volatile memory the registration position of the document feeder based upon an operator entering the identifying numeric indicia into the numeric data key entries of the copier.
U.S. Pat. No. 4,724,330 to Tuhro, assigned to Xerox Corporation, discloses a system which includes a raster input scanning device including a linear photoelectric sensor array and a movable carriage for moving an aperture card which contains information across the scanning array. The aperture card includes a target which is used by the scanning device to calculate Y-axis and X-axis offset values representative of the distances in the Y and X directions which the information on the aperture card differs from a predetermined location The offset values are used to discard data inputted from portions of the aperture card which do not contain any information.
A publication entitled "7650 Pro Imager IBM PC Compatible Service Manual", published April 1989, discloses on page 4-3 registration and skew adjustment of a document handler to a copying machine which utilizes a test document having a black edge. It appears as if the registration is manually adjusted.
U.S. Pat. No. 4,711,552 to Nilsson discloses an electrophotographic copier which synchronizes copy sheet gating, optic start of scan and document conveyor registration The start of scan of the optics assembly is effected by positioning a test master document having dark portions adjacent its leading and trailing edges on the platen, making a copy of the test master document, determining the length of undeveloped area adjacent to the leading edge of the copy, and adjusting the start of scan as a function of the determined length. These steps are done by visual inspection or by an optical sensor which is located downstream of the toner fixing station. The adjusting may be done electronically or mechanically.
U.S. Pat. No. 4,864,415 to Beikirch et al., assigned to Xerox Corporation, discloses a system for self-aligning a raster input scanner in a slow scan direction. The carriage is moved in the scan direction until sensed by a limit switch. Upon detection of the carriage by the limit switch, the carriage motion is reversed and the carriage is moved in the pre-scan direction over a target. The target, having a variable density image, is scanned until a preset target image line is obtained and the scan carriage position is registered. From this position, the carriage continues moving in the pre-scan direction until the length of the platen is scanned a predetermined number of scan lines. Then the carriage is reversed and moved in the scan direction to scan a document. Movement continues until the predetermined number of scan lines is counted at which time the image signals from the target are compared with the registration reference image. If a difference is detected, a fault flag is set. This procedure is carried out for every sheet to be copied and thus greatly decreases the efficiency of the machine.
U.S. Pat. No. 4,511,242 to Ashbee et al. discloses an electronic alignment of paper feeding components in a electrophotographic copier machine. Alignment is accomplished by placing an original master containing vernie calibrations on the document glass and a target master containing vernier calibrations in a copier paper bin. The machine is operated to produce a copy of the original master onto the target master to produce a double set of calibrations on the target master. When prepared, the copy provides information relating to skew angle, side edge registration and lead edge alignment of the image to the copy paper. This information is used to manually adjust the copier. Sensors are located in the copy paper path to automatically correct for deviations by calculating an average correction needed after a predetermined number of copies are made. This device compensates for the location of an original on a glass platen by adjusting the positioning of the receiving sheet relative to a photoreceptor drum.
U.S. Pat. No. 4,605,970 to Hawkins discloses a method and apparatus for calibrating an optical document digitizer.
U.S. Pat. No. 4,647,981 to Froelich, assigned to Xerox Corporation, discloses an automatic white level control for a raster input scanner. A circuit is provided to add a correction based on a predetermined correction curve for determining the amount of deviation of a light level from a desired level.
The disclosed apparatus may be readily operated and controlled in a conventional manner with conventional control systems. Some additional examples of control systems for various prior art copiers with document handlers, including sheet detecting switches, sensors, etc., are disclosed in U.S. Pat. Nos.: 4,054,380; 4,062,061; 4,076,408; 4,078,787; 4,099,860; 4,125,325; 4,132,401; 4,144,550; 4,158,500; 4,176,945; 4,179,215; 4,229,101; 4,278,344; 4,284,270, and 4,475,156. It is well known in general, and preferable, to program and execute such control functions and logic with conventional software instructions for conventional microprocessors This is taught by the above and other patents and various commercial copiers. Such software will of course vary depending on the particular function and the particular software system and the particular microprocessor or microcomputer system being utilized, but will be available to or readily programmable by those skilled in the applicable arts without undue experimentation from either verbal functional descriptions, such as those provided herein, or prior knowledge of those functions which are conventional, together with general knowledge in the software and computer arts. Controls may alternatively be provided utilizing various other known or suitable hard-wired logic or switching systems.
All references cited in this specification, and their references, are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features, and/or technical background.